Hello there cuties, I was hoping you could lend a rookie your expertise for a moment.

So, as you've probably already figured out I'm going to make a Len costume (from vocaloid), which will also be my first costume I might add!
BUT I'm having a hard time deciding whether I should have blonde/yellowish hair and stripes like the original has, or if I should go with a more golden/orangeish color instead which IMO looks better D:

Well, if you want to be more "accurate" I would say go yellow since that's the twins color. But if you like the contrast of the orange-yellow more then go with that. Vocaloid has a lot of leeway for colors.

Next time you should specify that the stripes are the sleeves. You had one run on sentence about the hour so no one would have known what you meant. I like the sleeves with the stripes personally but it's not up to us what you should wear. If you like them, do it, if you didn't then don't